1. Field of the Invention
The present invention relates to a method of producing calcium silicate-containing granulates having a density of at least 0.7 kg/dm3, by mixing a calcium oxide bound-containing product with a silicon-containing product, water and, if desired, a filler, subsequently forming granulates from said mixture and curing of the granulates obtained from said mixture by means of a heating treatment, while maintaining said granulates in a heated vapour atmosphere.
The density of the granulates is more particularly, more than 0.9 kg/dm3.
The term "granulate" should in this instance and in the following be understood as granules of each arbitrary shape being obtained by a pressing, extruding or granulating action and the like. The granules have a size corresponding to the size of normal gravel as used in concrete, which means more particularly, granules having a size of 2 to 40 mm diameter, more particularly, 2 to 32 mm diameter.
2. Description of the Prior Art
A method as described above has been used in the art. In this known method calcium hydroxide is mixed with sand and water and a filler, if any, whereupon the obtained granulates are cured in an autoclave by subjecting them to a steam pressure.
In order to prevent formation of cracks in the granulates which are cured by a steam pressure action, the respective known method is performed in three stages, heated steam being employed in the first stage until a pressure has been achieved of 0.8 ata stream pressure, a subsequent decreased steam pressure being employed in the second stage to e.g., 0.2 ata steam pressure the product in the third stage being heated by steam, by applying a pressure of, for example, 8 to 9 ata steam pressure.
During a curing action in this known method, steam will condense upon the granulates and will subsequently be discharged from the autoclave in the form of a flow of water. If any fillers are used, which contain harmful heavy metals, said harmful metals will be extracted during the condensation of the steam and will be discharged from the autoclave simultaneously with the flow of water, which gives rise to a serious inadmissible environmental pollution.
Additionally the flow of water escaping from the autoclave cannot be used directly for the preparation of fresh steam due to the aforementioned presence of pollutions derived from the harmful heavy metals in the granulates.
It is a further drawback of said known known method that it is rather difficult to perform the same, due to the application of three separate stages whilst, moreover, the prevention of cracks in the cured and hardened granulates is ineffective.